Basic magnesium carbonate and process of preparing same.



tlhll THEOPHIL SILBERMANN, O DRESDEN, GERMANY.

BASIC MAGNESIUM CARBONATE AND PROCESS OF PREPARING SAME.

No Drawing.

To alt whom it may concern:

Be it knownthat I, Dr. THEOPHIL SIL- BERIvIANN, chemist, subject of the King of Roumania, residing at Dresden, Germany, have invented a certain new and useful Basic Magnesium Carbonate and Process of Preparing Same, of which the following is a specification.

The present process for the preparation of a basic magnesium carbonate is based upon the direct precipitation of solutions of magnesium salts, such for example as the magnesium liquors of the potash industry, in the heat by an aqueous solution of am monia, which is treated with such a quantity of carbonic acid or mixed with such a quantity of ammonium carbonate (normal, sesqui or double carbonate) that a portion is still present as ammonium hydroxid and the other part is combined with carbonic acid to form normal ammonium carbonate.

The precipitation is always carried out in the heat and the degree of temperature to be employed varies with the proportions of NH and CO present in the liquid to be precipitated and which must be determined by experiment, and also although in a lesser degree, with the dilution of the solutions employed.

In order to obtain a good precipitation, temperatures above C. are generally necessary, and. in order to obtain a particularly voluminous magnesium carbonate, temperatures of from to 60 should be used,

while above 70 mostly denser precipitates, and below 40 basic carbonates richer in carbonic acid are obtained.-

An important point in the present process is the ratio between free ammonia and combined carbonic acid in the precipitating agent and, furthermore, the ratio between the magnesium of the solution to be precipitated on the one hand and the NH,, and CO of the precipitating agent on the other hand. In general there is in the precipitating agent at least 20% and at most 65% of the ammonia to be neutralized (to 'form (NHQ CO while in the reaction mixture the ammo-. nia must always be present in excess proportionally to the magnesium, the amount of carbonic acid does not amount to more than about 63 parts by weig it to 24'. parts nesium (ammonium magnesium carbonate Specification of Letters Patent.

Patented Dec. 7,1915.

Application filed June 29, 1914. Serial No. 848,056.

(NHQ,Mg(CO but must only be in moderate excess of the quantity necessary for combination of the whole of the magnesium to form basic carbonate and at the most up to the above given limits of 63 parts by weight of CO to 24 parts by weight of Mg. L

lVhen the above conditions are observed, there is obtained without any evolution of carbonic acid and by direct precipitation a basic magnesium carbonate, which even when working in very dilute solutions separates quantitatively and the precipitation of which is not prevented by the presence of ammonium chlorid, in contra'distinction to precipitations of magnesium salts bv means of NH, or (NHQ -CO under ordinary conditions. The basic magnesium carbonate, so obtained is also different from the basic carbonates found in commerce and considerably superiorto them in a technical respect. It is extremely voluminous, contains about per cent. of water of crystallization and is therefore much richer in water of crystallization than the known brands of commerce, loses the greatest part ofthe water at a low temperature, and'is also converted at a much lower temperature with separation of carbonic acid and water (at about 400 to 800) into a magnesia usta, that is, magnesium oxid (MgO) which like the magnesia carbonica possesses a much greater degree of fineness and particularly also a greater power of reaction than the ordinary article of commerce. Accordin to all experience hitherto gained, the use 0 the basic magnesium carbonate obtained by the present process affords very important advantages for the india-rubbcr industry.

Example: The Waste liquor of the potash industry, which is a waterysolution having "a strength of about 4C0 per cent,

is diluted down to about from t to 6 per cent. MgOl and then mixed with carbonated ammonia, containing about from 8 to 10 per cent. of ammonia and from 4 to 6 per cent. of carbonic acid and in such a manner that the carbonic acid for precipitation is present in very slight excess. Intimate mixture is eiiected, and the mixture is then heated to about from 45 to until after standing a short time or even during heating the entire mass assumes a curd-like consistency. After a short time, mostly in less than 15 minutes, ti e precipitation is complete and a h Ma, MgSO 0.5 K01 and 0.5% NaCl,

filtration may be performed at once. The product is well washed with water, dried and, if necessary disintegrated or pulverized in the ordinary way. The magnesia carbonica may then be converted into magnesia usta by heating or calcination in the well known way.

According to F resenius in his Guide to Qualitative Chemical Analysis 1874:, 14th edition, page 117, there is separated from solutions of magnesium salts, when these are mixed with ammonium carbonate (more rapidly from concentrated solutions, more slowly from dilute solutions) a precipitate which, according to the quantity of ammonium carbonate, consists of magnesium carbonate MgO.CO +3aq. or ammonium magnesium carbonate Nrnoco,+M o;co,+n

Addition of ammonia favors the precipitation verymuch. Ammonium chlorid acts against it, but is unable to prevent the formation of the precipitate with greater concentration. Fresenius mixed the solution of tlie magnesium salt with the commercial sesquicarbonate commonly used a reagent.

The acid magnesium carbonate, Mg (H00 ence of an excess of ammonia is a condition and the CO does not suflice for the formation of the double salt, all the magnesium is precipitated as basic carbonate, when the above conditions are obtained, without the evolution of carbonic acid, even invery dilute solutions, and even in the presence of ammonium chlorid.

What I claim is y l. The process for the preparation of basic magnesium carbonate, which consists in treating a magnesium salt solution with partly carbonated ammonia with the aid of heat, care being taken, that in the precipitating medium at least '20 per cent. but not vthe magnesium. in the shape of basic carbonate, there being however not more than 63 parts by weight of carbonic acid to 24 parts by'weight of magnesium.

2. The process for the manufacture of a basic magnesium carbonate, which consists in diluting effluents containing magnesium chlorid, then mixing it' with carbonated ammonia containing from 8 to 10 per cent. of ammonia and from 4: to 6 per cent. of carbonic acid, so that the carbonic acid is slightly in excess over the quantity neces sary for combining with the whole of the magnesium in the form of basic carbonate,

heating the mixture until it assumes a curdlike consistency, then filtering and drying the product, substantially as described.

3. Asa new product, basic magnesium carbonate, being an extremely voluminous granular material, containing about fifty per cent. of water of crystallization, and capable of being converted into a magnesia usta by heating to a temperature between 400 and 800 C., while giving off carbonic acid and water, substantially as described.

In testimony whereof I have hereunto set my hand in presence of two subscribing wit-' nesses.

DR. THEOPHIL SILBERMANN Witnesses:

WOLDEMAR HAUrT, TIENRY HAsPEn.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner ofjEatenta Washington, D. C. 

